Hydraulic servo control apparatus



1, 956 A. H. WILKINSON 2,759,457

HYDRAULIC SERVO CONTROL APPARATUS Filed May 11 1951 2 Sheets-Sheet 1 INVEN TOR. F/ l fl/V/n hf M'lt/nson Aug. 21, 1956 A. H. WILKINSONHYDRAULIC SERVO CONTROL APPARATUS 2 Sheets-Sheet '2 Filed May 11, 1951I//////////////////////IV////////// Hfforr/e L United States PatentHYDRAULIC SERVO CONTROL APPARATUS Alvin H. Wilkinson, Tulsa, 01:121.,assignor, by mesne assignments, to Cabot Shops, lnc., Boston, Mass., acorporation of Massachusetts Application May 11, 1951, Serial No.225,776

2 Claims. (Cl. 121-41) This invention relates to brakes, and moreparticularly, but not by way of limitation, to a hydraulic control for apneumatic powered brake or similar apparatus. This application is acontinuation-in-part of applicants c0- pending application, SerialNumber 112,680 filed August 27, 1949, now Patent No. 2,705,059, andentitled External Brake.

The present invention contemplates a hydraulic control system for anexternal brake such as shown in said co-pending application and isparticularly concerned with the problem of notifying the operator of thebraking action being supplied and providing a more sensitive feed forthe brake operator. A novel hydraulic circuit is interconnected to theactuating handle, air valve and air actuator in such manner that theposition of the actuating handle notifies the operator of the brakingaction being applied and positioning of the handle determines thebraking action being applied.

An important object of this invention is to provide a hydraulic controlfor a brake to notify the operator of the braking action being applied.

Another object of this invention is to provide means for assuring theapplication of a predetermined braking action for each setting of theactuating handle.

A further object of this invention is to provide means for controllingthe operation of the air valve of a pneumatic braking apparatus.

An additional object of this invention is to provide a novel hydrauliccontrol system utilizing a movable master cylinder operable by acombination of mechanical and hydraulic forces.

A still further object of this invention is to provide an efficienthydraulic control for a braking apparatus having a long service life andwhich may be economically manufactured.

Other objects and advantages of the invention will be evident from thefollowing detailed description, read in conjunction with theaccompanying drawings, which illustrate my invention.

In the drawings:

Figure 1 is an elevational view of a braking apparatu having a novelhydraulic control thereon.

Figure 2 is a partial sectional view of the hydraulic control shown inFigure 1.

Figure 3 is a sectional view, partially in elevation, of the airactuator.

Referring to the drawings in detail, and particularly Fig. 1, referencecharacter 4 designates a rotatable drum such as a hoisting drum or thelike, rotatably supported by legs 5 on a stationary base 6. A brake band7 preferably of the type shown in applicants above-mentioned co-pendingapplication encircles the drum 4. The band 7 is pivotally secured (notshown) at one end 8 thereof to a stationary plate 9 carried by the baseportion 6. A suitable bracket 10 is secured to the opposite end 11 ofthe brake band 7 for connection with a horizontally disposed rod 12. Therod 12 is adapted to be 2,759,457 Patented Aug. 21, 1956 ice to Fig. 1)to alternately appply and release the brake band 7 on the drum 4 as willbe more fully hereinafter set forth.

The 'rod 12 extends into an air actuating cylinder '13 suitablysupported (no-t shown) on the stationary base 6. A plurality of supoprtrods 14 extend outwardly from the cylinder 13 in parallel relationshipto the rod 12 to support an apertured and stationary plate 15 loosely onthe rod 12. A second plate 16 is provided with a plurality of apertures(not shown) for receiving the rods 14 and is adapted to move along therods 14 as will hereinafter set forth. The plate 16 is rigidly securedto the rod 12. A helical spring 17 is provided around the rod 12 betweenthe plates 15 and 16 and is anchored at its opposite ends to the plates15 and 16. It is readily seen that the spring 17 constantly urges theplate 16 and rod 12 to the right to apply the brake band 7 on the drum4.

As clearly shown in Fig. 3, a plunger or pressure plate 18 is secured tothe outer end 19 of the rod 12 within the air actuating cylinder 13. Theplunger 18 is adapted to be moved to the left by air pressure and ismoved to the right by the action of the spring 17. A suitable conduit 20is connected at one end to the rear end 21 of the cylinder 13 and atopposite end to an air valve indicated generally at 22 (Fig. 2).

The air valve 22 comprises a housing 23 having three chambers 24, 25 and26 therein. A partition 27 having a port or aperture 28 in the centralportion thereof separates the chambers 24 and 25. A flexible diaphragm29 suitably secured in the housing 23 separates the cham-.

bers 25 and 26. Air under pressure is constantly supplied to the chamber24 through a suitable conduit 30 from any desired source (not shown). Aby-pass conduit 31 is interconnected to the chamber 24 and the chamber26, thereby also providing a constant supply of high pressure air to thechamber 26 for purposes as will be hereinafter set forth. The conduit 20com- Furthermore, the valve 34 is secured on a valve stem 36 extendingfreely through the port 28 and having another valve 37 on the inner endthereof.

A tubular stem 38 extends through the diaphragm 29 and is securedthereto by suitable reinforcing plates 39 and 40 in the usual manner.The stem 38 is adapted to contact the valve 37 and move the valve 34away from the port 28 as will be hereinafter set forth. A circularshaped piece of sealing material 41 is carried by the valve 37 forsealing off the inner end of the stem 38 as will be hereinafter setforth. A plurality of transverse apertures 42 are provided in the outerend of the stem 38 to establish communication between the central bore43 of the stem 38 and the interior of a stationary sleeve or guide 44.An exhaust port 45 is provided transversely in the inner end of thesleeve 44 to provide an exhaust of air from the central chamber 25 inone position of the stem 38 as will be hereinafter set forth.

The diaphragm 29 is adapted to reciprocate in the valve housing 23 andis constantly urged into the cham-.

ber 25 by a suitable spring 46 co-acting with the valve housing 23 andthe reinforcing plate 48. The diaphragm 29 is also constantly urgedtoward the central chamber 25 by the high pressure air in the chamber26.

A tubular sleeve 47 is formed on the outer end of the stem 38 and isadapted to reciprocate in the stationary sleeve-44 during operation ofthe valve 22 as will be hereinafter set forth. The outer end 48 of thetubular sleeve 47 is disposed exteriorly of the stationary sleeve 44 andis internally threaded to receive a master cylinder indicated generallyat 49. A spring 47a is disposed in the. sleeve 47 and operates as a lockto firmly secure the cylinder 49 in the sleeve 47.

The master cylinder 49 comprises twocup-shaped members 50 and 51threadedly interconnected as clearly shown in Fig. 2 to form asubstantially cylindrical chamber 52. A piston member 53 is reciprocallydisposed in the chamber 52 and has a sealing ring 54 in the outerperiphery thereof adapted to remain in sealing contact with the innerperiphery of the chamber 52. A circumferential shoulder 55 is providedin the cup-shaped member 51 and a-circumferential shoulder 56 isprovided in the cup-shaped member 50 to provide stops for the piston 53and limit the reciprocating movement thereof in the chamber 52. Anaperture 57 is provided in the central portion of the piston 53 toloosely receive an actuating rod 58. The rod 58 may be movedlongitudinally through the aperture 57 as will be hereinafter set forth.A circular shaped head 59 is provided on the inner end of the actuatingrod 58 and has a sealing ring 60 therein adapted to contact the piston53 and seal off the aperture 57 in one position of the rod 58. The head59 obviously limits the outward movement of the rod 58 independent ofthe piston 53. A suitable helical spring 53a surrounds the rod 58 and isanchored at its opposite ends to the plunger 53 and cupshaped member 51to constantly urge the plunger 53 into contact with the head 59. The rod58 extends outwardly from the head 59 through an aperture 51a providedin the cup-shaped member 51. A suitable sealing ring (not shown)v .ispreferably provided in the aperture 5.1a around the rod 58 to precludeleakage of fluid from the chamber 52.

The outer end 61 of the rod 58 is suitably hinged to a triangular-shapedarm 62 The arm 62 is in turn pivotally secured to a stationary bracket63. An actuating handle 64 is also secured to the arm 62 and in spacedrelation to the outer end 61 of the rod 58. It will be apparent thatrotative movement of the handle 64 is transmitted through the arm 62 tothe rod 58 for actuating the piston 53 and air valve 22 as will be morefully hereinafter set forth.

A hydraulic fluid supply chamber 65 is secured on the cupsshaped member50 and communicates through a port 66 with the chamber 52. Thefluidsupply chamber 65 is preferably substantially filled with asuitable hydraulic fluid .to. maintain a constant supply of hydraulicfluidto the inner end 67 of the chamber52. A threaded aperture 68 isalso provided in the cup-shaped member 51 adjacent the outer end 69 ofthe chamber 52. One end of a suitable flexible conduit 70 is secured inthe aperture 68 and the opposite end thereof is secured to one endofaslave cylinder 72 as clearly shown in Figure 3. The slave cylinder 72issecured in the air actuator 13 in parallel relationship with the rod 12.A plunger 73 is reciprocally disposed in the .slave cylinder 72 and isadapted to protrude'from the cylinder 72 into contact with the airactuator plunger 18. Abody of hydraulic fluid is retained in the slavecylinder 72, conduit 70 and chamber 52 of the master cylinder 49 toactuate the slave plunger 73 in one direction upon movement of themaster plunger 53. The plunger 73 is moved in the opposite direction bythe air actuator plunger 18 as will be more fully hereinafter set forth.

Operation As previously set forth, high pressure air is constantlysupplied through the conduit 30 to the outer chamber 24, and'through theby-pass conduit 31 into the chamber 26. Assuming the valve 22 is set asshown in Fig. 2,the valve 34'is slightly-retracted; therefore, the highpressure air will also flow from the chamber 24 through a transverseport 75, provided in the inner end of the guide 33, and hence throughport 28 into the central chamber 25. It w'illalso be noted that theinner end of the stem 38 is in contact with the seal 41 of the valve 37.Therefore, thehighpressure air cannot escape through the bore 43 of thestem 38, apertures 42 and exhaust port 45. The high pressure air isconstrained to flow from the chamber 25 through the conduit 20 into theend 21 of the air actuator 13 to press the plunger 18 to the left (Fig.3) against the action of the spring 17 (Fig. l). The brake band 7 isthereby removed from the drum 4 to release the drum for free rotation.As long as the valve 22 is retained in a position as shown in Fig. 2, aconstant supply of high pressure air is directed as above set forth intothe air actuator 13 to retain the brake band 7 in a released position.

When it is desired to apply the brake band 7 to the drum 4, the handle64 is moved slightly in a clockwise direction. The actuating rod 58 isthereby moved to the right and since the head 59 is in contact with themaster plunger 53, the master plunger 53 will also be moved to theright. Furthermore, the slave plunger 73 (Fig. 3) is in contact with theair actuating plunger 18. Therefore, the hydraulic fluid cannot beexhausted from the chamber 52 of the master cylinder 49 because of theair pressure against one side of the piston 18 prevents movement thereofuntil relieved and provides a static fluid lock between the plunger 53and the master cylinder 49. Hence the cylinder 49 is movedsimultaneously to the right with the movement of the rod 58 and plunger53 to actuate the sleeve :47 and remove the valve stem 38 from the valve37 In this condition of the air valve 22, communication is establishedfrom the central chamber 25 through the bore 43 of the stem 38, theapertures 42, and exhaust port 45 to atmos,

pheric pressure. In addition, the high pressure air in thechamber 24will force the valve 34 to the right into a closed position over theport 28. Therefore, the air previously supplied to the air actuator 13is exhausted through conduit 20, chamber 25, passageway 43, apertures42, and exhaust port 45. The helical spring 17 (Fig. 1) will thenoperate to force the plate 16 and rod 12 to the right and apply thebrake band 7 to the drum 4.

It will also be noted that the chamber 25 will then be at low pressurewhile the chamber 26 is retained at high pressure. Therefore, the highpressure air in the chamber 26 co-acting with the helical spring 46 willtend to urge the diaphragm 29 and hence the stem 38 to the left. Thisforce is transmitted through the stem 38, sleeve 47 and master cylinder49 to retain the hydraulic fluid in the chamber 52 to the right of theplunger 53 under pressure, it being understood that the handle 64 andhence the plunger 53 are retained in a fixed position. The pressureexertedon the hydraulic fluid by movement of the sleeve 47 will providea greater pressure to force the slave plunger 73 to the right to followthe air actuating plunger 18. As the slave plunger '73 moves to theright, whereby the volume between the cylinder chambers 72 and 52 is,increased so that the hydraulic fluid is exhausted from the chamber 52to permit a movement of the master cylinder 49 to the left. It will beapparent that the diflerential air pressure acting on the diaphragm 29transmits a force to the sleeve 47, and through the fluid lock in thechamber 52 the force is transmitted to the plunger 53, the vrod 58, thearm 62 and to the lever 64. This force transmitted ,to the lever orhandle 64 provides a feel force for the operator in accordance with theapplication of the brake band 7. When a partial braking action isattained, .however, the hydraulic apparatus also positions the valve221, and is, therefore, in part at least, a control system. If theoperation of the apparatus relied only on air pressure, the operatorthereof would be unable to determine the amount of braking actionapplied because air is compressible and the handle 64 could be movedfurther after full application of the brake.

When the cylinder 49 has reached substantially the position shown inFig. 2, the stem 38 will again be in contact with the valve head 37 topreclude a further ex.- haust ofair from the air actuator 13 andcentralchamber 25. In the event the brake band 7 has not been fullyapplied, the force exerted by the spring 17 will be equalized by theforce exerted by the air remaining in the air actuator 13 to retain theplunger 18 in a fixed position and preclude further movement of theslave plunger 73. The hydraulic fluid in the slave cylinder 72, conduit70 and chamber 52 will again become static to preclude a furthermovement of the master cylinder 49 to the left and hence an opening ofthe air valve 22. As long as the actuating handle 64 is retained in thisposition, the air pressure in the air actuator 13 will remain constantto maintain a predetermined braking action of the brake band 7.

Assuming the handle 64 is again moved in a clockwise direction to themaximum degree, the master cylinder 49 will again be moved to the rightthrough the medium of the hydraulic fluid in the chamber 52 to removethe valve stem 38 from the valve head 37 and permit a further exhaust ofair from the air actuator 13. The spring 17 will obviously again movethe rod 12 and plunger 18 to the right and fully apply the brake band 7on the drum 4. Furthermore, the diaphragm 29 will be urged to the leftas set forth above to retain the hydraulic fluid present in the chamber52 and slave cylinder 72 under pressure. The slave plunger 73 will againbe moved to the right simultaneously with the air actuating plunger 18to permit an exhaust of hydraulic fluid from the chamber 52. The mastercylinder 49 is then moved to the left in the same manner as set forthabove. However, since the brake band 7 is fully applied on the drum 4,the plunger 18 will be moved the maximum extent to the right in the airactuator 13. Therefore, the slave plunger 73 is moved to the right to agreater degree than set for above to permit a greater exhaust ofhydraulic fluid from the chamber 52. In this manner, the shoulder 55 inthe cupshaped member 51 will contact the plunger 53 during the movementof the master cylinder 49 to the left to retain the valve stem 38removed from the valve head 37. Continuous communication is therebyprovided between the air actuator 13 and the exhaust port 45 tofacilitate.

the continuous action of the spring 17 in applying the brake band 7.

When it is desired to partially release the brake band 7, the actuatinghandle 64 is moved in a counterclockwise direction a predetermineddegree. The rod 58 is thereby moved to the left to release the mastercylinder 49 for movement to the left by the action of the high pressureair in chamber 26 coacting with the spring 46 on the diaphragm 29. Asset forth above, the spring 53a retains the plunger 53 in contact withthe head 59, therefore, the rod 58, plunger 53 and cylinder 49 are movedsimultaneously to the left. The stem 38 is thereby moved to the positionshown in Fig. 2 to contact the valve head 37 and remove the valve 34from the port 28. It is then readily seen that the high pressure airwill again flow from the chamber 24 through the port 28, central chamber25 and conduit 20 to the air actuator 13. The high pressure air in theactuator 13 will overcome the force exerted by the spring 17 and forcethe plunger 18 along with the slave plunger 73 to the left.

The slave plunger 73, in moving to the left, forces hydraulic fluid fromthe slave cylinder 72 through the conduit 78 into the outer end 69 ofthe chamber 52. Since the plunger 53 will then be in contact with thehead 59, the hydraulic fluid being introduced into the outer end 69 ofthe chamber 52 will react on the cup-shaped member 51 to force themaster cylinder 49 to the right, it being understood that the actuatinghandle 64 is held in a predetermined position by the operator to fix theposition of the rod 58. The valve stem 38 is therefore also moved to theright to release the valve head 37 and permit movement of the valve 34into closing position over the port 28. Further flow of high pressurefluid to the air actuator 13 is thereby prohibited. The air remaining inthe actuator 13 will exert a suificient force to 6 equalize the forceexerted by the spring 17, and retain the air actuating plunger 18 in afixed position. Movement of the slave plunger 73 to the left will alsotherefore be stopped to preclude a further introduction of the hydraulicfluid into the outer end 69 of the chamber 52.

In this manner, the movement of the master cylinder 49 is stopped toposition the valve stem 38 into contact with the valve head 37 in such aposition that the valve 34 will be in a closed position over the port 28and the sealing member 41 will be in closed position over the bore 43 ofthe stem 38. When the brake band 7 is in this partially releasedposition, the plunger 53 will be positioned in an intermediate positionin the chamber 52 in spaced relation to the shoulders 55 and 56.

Further movement of the actuating handle 64 in a counterclockwisedirection will result in a similar addition of air pressure to the airactuator 13 to overcome operation of the spring 17 and completelyrelease the brake band 7 from the drum 4. When the brake band 7 iscompletely released from the drum 4, the master plunger 53 will be inthe position shown in Fig. 2, that is, in contact with the shoulder 56.Upon further movement of the handle 64 in a counterclockwise direction,the rod 58 is moved to the left through the plunger 53 to providecommunication between the opposite ends of the chamber 52 through theaperture 57. In this condition, any surplus fluid in the hydrauliccircuit (designated by the chamber 52 to the right of the plunger 53,the conduit and slave cylinder 72) will be exhausted through aperture 57into the end 67 of chamber 52 and reservoir 65. In the event of adeficiency of fluid in the hydraulic circuit, which may be due to leaksor fluid contraction, fluid will flow from the reservoir 65 and end 67of chamber 52 through the aperture 57 to replenish the fluid in thecircuit.

From the foregoing, it is apparent that the present invention provides anovel hydraulic control for a pneumatic braking apparatus wherein theposition of the actuating handle predetermines the amount of brakingaction applied. Hunting, that is, juggling or frequent moving of theactuating handle to obtain a desired braking action, is therebydispensed with. When the operator positions the actuating handle apredetermined braking action is assured. It is also apparent that thepresent invention provides a novel hydraulic control system utilizing astationary slave cylinder and a movable master cylinder. Furthermore, aneflicient hydraulic control is provided, having a long service life,Which may be economically manufactured.

Changes may be made in the combination and arrangement of parts asheretofore set forth in the specification and shown in the drawings, itbeing understood that any modification in the precise embodiment of theinvention may be made within the scope of the following claims withoutdeparting from the spirit of the invention.

I claim:

1. In combination with an air actuated cylinder for use with a brakeband or the like, comprising an air operated plunger reciprocable insaid cylinder, an air valve mecha nism connected to the cylinder tocontrol movement of the plunger, a control handle cooperating with thevalve mechanism to cause actuation thereof, a diaphragm member disposedwithin the air valve mechanism and exposed to air pressure differentialstherein, a movable stern extending through the diaphragm and adapted formovement therewith in one direction to open the valve for supplying airpressure to the air cylinder and in an opposite direction to close thevalve for exhausting air pressure from the air cylinder, a hydraulicmaster cylinder carried by the stem and movable simultaneous therewith,a master plunger reciprocab'le in the master cylinder, a slave cylinderdisposed in the air cylinder, a slave plunger reciprocably disposed inthe slave cylinder and adapted to contact the air plunger, meansinterconnecting the master and slave cylinder providing hydraulicpressure therebetween, said master plunger manually moved to apply fluidpressure against the slave plunger for moving it in one directionagainst the air operated plunger to provide a fluid lock, said handleconnected to the master plunger and adapted to be initially moved tocause movement of the valve stem for operation of the valve toalternately supply and ex haust air pressure from the air cylinder, andsaid handle responsive to the feel provided by the fluid lock and airPressure diiferentials acting upon the diaphragm to control movement ofthe valve stem and determine the amount of force applied by the airoperated plunger.

2. The combination ,of an air cylinder, a plunger reciprocally disposedin said cylinder and adapted to be moved in one direction by airpressure, means constantly urging said plunger in an opposite direction,an air valve mechanism controlling application of air pressure to saidcylinder to move said plunger in the first mentioned direction, adiaphragm member disposed within the valve and exposed to air pressure,diiferentials, a cylindrical stem extending into the valve mechanismand through the diaphragm to be biased thereby for opening the valve tocause movement of the plunger in the first mentioned direction, saidstem member controlling the operation of the valve and whereby the valveis alternately opened to supply air pressure to the air cylinder andclosed to permit air pressure to exhaust from the cylinder, meansconstantly urging the stern toward a closed position for the valve, ahydraulic master cylinder carried by the stem, a slave cylinderhydraulically interconnected to the master cylinder, a slave plunger inthe slave cylinder adapted to be moved in one direction by the firstmentioned plunger and in the opposite direction by fluid pressure, amaster plunger in the master cylinder manually moved to apply fluidpressure against the slave plunger for moving it in one directionagainst the air pressure in the air cylinder to provide a fluid lock,said master plunger adapted to move the stem to a position providing forthe exhaust of air through the valve mechanism, whereby the firstmentioned plunger is moved in said opposite direction to providehydraulic movement of the slave plunger and a release of hydraulic fluidfrom the master cylinder in such a manner to release the stem formovement to a closed position, a handle for manually moving the masterplunger and responsive to the feel provided by the fluid lock to controlmovement of the valve stem and determine the amount of force applied bythe first mentioned plunger.

References Cited in the file of this patent UNITED STATES PATENTS971,377 Herr Sept. 27, 1910 1,594,942 Guernsey Aug. 3, 1926 1,753,370 DuPont Apr. 8, 1930 2,270,431 Freeman Jan. 20, 1942 2,308,299 Page -n Jan.12, 1943 2,328,637 Freeman Sept. 7, 1943 2,342,878 Majneri Feb. 29, 19442,352,357 Almond June 27, 1944 2,589,850 Orelind'et al. Mar. 18, 1952

